Blood pressure may be sodium-dependent in diabetic patients without overt nephropathy

Summary  We studied 29 normotensive diabetic patients free of long-term complications (13 insulin requiring and 16 noninsulin requiring), and 54 normotensive control subjects. No diabetic patient had overt nephropathy (in all 24 h urinary albumin excretion was <0.5G and Albustix was negative), but 24 h urinary albumin excretion was significantly higher than in control subjects in both insulin requiring and non-insulin requiring patients. Exchangeable sodium was increased in both insulin requiring and non-insulin requiring diabetic patients, compared with control subjects, and was similar in the two diabetic groups. Plasma renin activity was lower in non-insulin requiring patients than in control subjects, but was not different in insulin requiring patients and controls. Exchangeable sodium was significantly related to systolic and diastolic blood pressure in non-insulin requiring diabetic patients but was not related in insulin requiring patients or in control subjects. Exchangeablt sodium was positively related to 24 h urinary albumin excretion in each diabetic group. We conclude that sodium retention occurs in diabetic patients before the development of overt nephropathy. Recent evidence indicates that overt nephropathy is preceded by a phase of incipient nephropathy, when urinary albumin excretion is elevated and there is a small rise in blood pressure. The associations between body sodium and both blood pressure and 24 h urinary albumin excretion in non-insulin requiring diabetic patients suggest that blood pressure may become sodium dependent before the development of overt nephropathy in this group. This could contribute to the blood pressure rise in incipient nephropathy.